Cushioned push bench



May 22, 1934. H. MP 1,959,425

CUSHIONED PUSH BENCH Filed Mafch" 23. 1932 Fig.2

"f EllllilllllillllilllllllFlllElllEl a MOT R Inzren for y M un-M! Patented Ma 22, 1934 UNITED STATES V I v 1,959,425 CUSHIONED PUSH BENCH Heinrich Heetkamp, Duisburg, Germany, assignor to Demag Aktiengesellschaft, Duisburg, Germany Application March 23, 1932, Serial No. 600,778 r In Germany April 2, 1931 Y 4 Claims.

The invention relates to aidraw bench for the manufacture of seamless tubes or tubular bodies of the kind in which a hollow'body with thick walls is forced, by the use of a mandrel, through a series of draw rings or other shaping tools disposed one behind the other.

The mandrel carrier (mandrel shaft) is usually driven by means of a rack, the pinion of which is driven by an electric motor. In view of the long stroke of the mandrel, the rack is operated at relatively high speed in order to ensure smoothness in operation.

These high speeds are desirable in order to reduce to a minimum the loss of heat during the drawing process. In treating special steels which can be shaped only within a definite narrowrange of temperature heat losses should be avoided.

Difllculties arise in practice owing to the necessity for stopping the mandrel as quickly as possible after the work has passed through the last draw ring. A long idle run at the delivery end is disadvantageous as it means loss of time.

.To'meet these requirements the tube-drawing benches are usually driven by a reversible motor controlled by an Ilgner apparatus. This enables the motor to be reversed during the for ward movement of the rack and thus to brake the masses electrically. In spite of the expensive Ilgner apparatus th control is not sensitive and the greatest care is needed on the part of the operator in charge to avoid damage to the draw bench.

The older apparatus were frequently so constructed that the motor driving the bench was allowed to run continuously, the forward and return movements of the rack being effected by means of clutches and worm gearing. The' rate of travel in benches of this kind is relatively low, such clutches being very liable to give rise to trouble through being almost continuously slipped in and out.

Another disadvantage is that the speed cannot be controlled during the forcing of the work fed from a specially provided hydraulic main, in

order to provide a greater stripping power than can be normally furnished by the motor.

This arrangement ensures a more reliable and advantageous travel of the rack than can be obtained with Ilgner apparatus. Further an ordinary polyphase or direct-current motor can be employed, the expensive Ilgner apparatus being dispensed with. The working capacity of the draw bench is also greater than could ordinarily be obtained from the driving gear and rack.

The invention is diagramatically illustrated by way of example inthe accompanying drawing. I

Figure 1 shows the driving gear of the rack, and also the hydraulically operated buffers.

Figure 2 shows the mandrel shaft, mandrel and the draw ring bed, parts not shown in Figure 1.

Figure 3 is a plan corresponding to Figure 1, the "member (rack) carrying the mandrel. shaft being in the starting position.

Figure 4 shows the rack in the end position. The rack 1, which is guided in known manner, gears with the driving pinion 2 which is rotated through reducing gear 20 from an electric motor 21, whichis reversible or is provided with reversing gearing and may be adapted to be clutched and unclutched from the driven elements. The mandrel'shaft 4 is mounted on the rack 1 at 3, and'the mandrel 5 is disposed at one end of said shaft. 6 is the billet (Figure 2) shown in position for treating. l is the draw ring bed. 4

8 and 9 denote hydraulic cylinders provided in pairs, the plunger rods 11 and 12 of which serve to absorb the thrust of the rack 1. The two pairs of cylinders are inconnection vwith a common expansion vessel 13 for the fluid pressure medium. The common communication pipe 14 is provided with non-retum valves 15 which are self-closing under pressure but may also be positively opened by means of levers 22, 23 coupled together by a rod 24, under control of a hand .lever 25. 16 are the buffer stops for the plunger rods 12, the member connecting themwith the rack 1 being indicated by 1'7. 18 are stops provided on the rack 1 for the plunger rods 11.

by the rotation of the pinion 2 by the motor 21. The mandrel 5 forces its wayinto the billet and then presses it through the draw rings ,of the bed 7 in known manner. After having passed right through the draw ring bed the mandrel, together with the work (tube) that has been drawn over it is in the position indicated by broken lines in Figure 2 beyond the draw ring bed. In this position the mandrel, with the tube upon it detaches itself from the shaft 4 and is carried forward along conveyors for further treatment; alternatively, and especially in the case of tubes made from the special steels, the mandrel remains secured to the shaft and, after a stripping device has been inserted around the mandrel shaft between the draw bench and the tubes, is drawn out of the tube by reversing the direction of movement of the rack. In apparatus as usually employed, after the tube has been forced through the last draw ring, the bench must be stopped at once, as otherwise the rack 1 will strike against the draw ring bed 7 and will inevitably damage the machine. The moving masses however are very large so that the danger remains even if the Ilgner apparatus is used. According to the invention the stops 16 come into contact with the plunger rods 12 during the last stage of the forward movement of the rack. The plunger rods 12 are subjected to the pressure of the fluid medium present in the communication pipe 14, but are resilient as an air cushion is provided in the expansion vessel 13. The further the plunger rods 12 are forced into the cylinders 9, the greater will be the resistance which can be adjusted by adjusting the air cushion. Either before, or during the forcing back of the rods 12 the motor is switched off, and is brought to a standstill very quickly by the counter pressure exerted by the rods. The rods then immediately transmit the stored up force in the expansion vessel 13 and reverse the direction of movement of the rack and the motor, thereby greatly reducing the amount of work required to reverse the motor. As the rack approaches the initial position the stops 18 engage the plunger rods 11 and drive them into the cylinders 8 against the pressure of the fluid medium which serves to cushion the rack and bring it to a standstill. As however the rack must remain in the rear position unt l a new billet 6 and possibly also a new mandrel 5, has been inserted, the force stored up in the cylinders 8 is held in check by means of a non-return valve 15. This valve opens immediately the motor is switched on, or if a continuously'running motoris" employed,

when the clutch and reversing gearing are slipped in. In such case, also, the stored up force is completely applied to the advancing rack. Moreover, in special instances the pipe 14 maybe connected at 19 .with a separate hydraulic main so that-for the purpose, for example of stripping the tightly shrunk tubes from the mandrelsuch pressure can be transmitted to the cylinders 9 so as to raise their impelling force if desired above the force of the driving motor. By these means not only'is economical working assured, but also possibilities are afforded of substantially exceeding the normal range of use of the draw bench without the need for strengthening the bench itself. During the additional work hereinbefore referred to the teeth of the rack and the pinion and gearing are almost completely relievedof strain although the stripping force might be considerably greater than the teeth of the rack mechanism would .stand in the ordinary way.

I claim:

1. A draw bench for the manufacture of seamless tubes, comprising an electrically operated mandrel drive, a mandrel carrier operated by the said drive, a mandrel supported upon the said carrier, .a plurality of draw rings in operative relation to said mandrel, fluid pressure cylinders disposed in fixed positions respectively adjacent the ends of the travel of the mandrel carrier, plungers within the said cylinders, the rods of which project adjacent the path of the mandrel carrier in a direction towards one another, elements upon the mandrel carrier to engage the said plungers at the respective ends of the travel of the mandrel carrier, and afluid pressure accumulator connected with the said cylinders.

2. A draw bench according to claim 1, comprising self-closing members such as non-return valves disposed intermediate the respective cylinders and the fluid pressure accumulator for controlling the recoil force exerted by the cylinders through the plungers.

3. A draw bench according to claim 1, comprising self-closing members such as non-return valves disposed intermediate the respective cylinders and the fluid pressure accumulator for controlling the recoil force exerted by the c31- ihders through the plungers, mechanical elements for respectively opening the said selfclosing members positively, the said mechanical elements being coupled together and a controlling element connected to and operating the said mechanical elements.

4. A draw bench according to claim 1, provided with a source of fluid pressure and means connecting the said source of fiuid pressure with the said cylinders for the purpose of increasing the pressure of the fluid medium within the cylinders above that provided by the accumulator.

HEINRICH HEE'IKAMP. 

